Gas producing compositions



Unitcclstates Patent F 1 Claim. c1. sz-asr The present invention relatesto new and: improved gas agent.

producing compositions of the kind capable in compressed condition ofpropagating -s'elfsustained non detonating gas producing decompositionthrough themselves whenlo callyheated.

For some applications itis essential to employ igas pror "ducing chargesgiving rise to gases whichdo 'not'centain large proportions either ontheone handaof free oxygen or oxides of nitrogenor on the other hand ofoxygen cons'uming' products-such as carbon' monoxide, hydrogen,hydrocarbons, or ammonia. Compositions of this type may consist ofanoxidant, suchas ammonium'nitrate and/ or potassium nitrate in admixturewith air-appropriate quantity of an organic fuel, for example, guanidinenitrate or nitroguanidine,'together witli one. or more sensitisers ofthe thermal decomposition-of the-mixture. The sensitising agents in thecase of these particular fuels may include puiverulent copper andcopper-com ounds, ichrorates andpolychromates, for example; potassiumchrornate or ammonium" dichromate. The'decompositibn' of mixtures ofthis type produces gases at very high temperatures which even in thecase of fuels whose oxygen deficiencies are comparatively low, as in thecase of the two above named compounds are of the order of 1800- 2000 C.For certain applications, however, such high temperatures cannot betolerated and charges are required giving gases of similar character atsubstantially lower temperatures than result from the use of the oxidantand the fuel with the sensitiser Without a cooling agent.

It was to be expected that inorganic carbonates which decomposeendothermically, could be used as cooling agents but we have found thatthe burning rate of pellets of compositions containing magnesium andcalcium carbonates artificially prepared by precipitation from solutionsof soluble magnesium or calcium salts were very low, and that if morethan 15-20% of such a carbonate was included in the composition, thepellets were extremely difiicult to ignite and were not capable of selfsustained decomposition at atmospheric pressure. Furthermore,consolidation of charges of compositions containing these cooling agentswas poor, the charges frequently exhibiting radial cracks, a fault whichcould not be overcome by granulation of the powder. In addition, theintroduction of the so prepared carbonates in the composition loweredthe stability on hot storage.

We have now discovered that by using in admixture with the aforesaidoxidant, the organic fuel, and the sensitiser, the naturally occurringmagnesium carbonates dolomite or magnesite, gas producing compositioncan be obtained which may be ignited and decomposed in a satisfactorymanner, which consolidate well on pressing, and which have thermalstabilities similar to those of the parent compositions containing nocooling agent. The naturally occurring magnesium carbonates have ahigher bulk density than the precipitated carbonates, which may be afactor affecting the capacity of the mixture for consolidation. Othernaturally occurring carbonates, e.g. calcite and chalk, also have higherbulk densities than ice 2 the synthetic compounds but the stability ofgas producing compositions containing these ingredients cool ngagenftsis interior to that of similar compositions containingjfdelemiteoi ma nesite as coming agent's. I,

Ifithe case vi -tiers the gas producing com osition coinp isessensitised mixture oraiiimoiiinni nitrate, potassiurii nitrate anduanidiiie nitrate and roduce only a small percentage of oxygen consuminggases or fre'e oxyg n orpxid es' of nitrogen iii the eons prieduets upto or dolomite or magnesite may befusd as cooling In "preparin thecompositions of the present invention, since the addi on of con g a entsreduces the rate of burning ornie composition, it be necessary, bysnitably choosing the proportion of cooling agent, to strike acompromise between the desired amount of cooling and the maintenance ofa desired burning rate. The rates of reaction and the gas temperature ofmixtures containing different proportions of cooling agent aredetermined at the required operating pressure, and the most suitablecomposition is selected v The invention is further illustrated by therenewing examples in which parts of solid ingredients are by weight.

Example -1 -A gas producing composition was) made by intimately mixing}together the following powdered iiigredients' z Dolomite Ammoniumdichromate Copper oxalate Parts by volume Ammonia 1.3 Oxides of nitrogen1.4 Carbon dioxide 26.7 Oxygen 0.9 Hydrogen 1.3 Carbon monoxide 1.8Nitrogen 66.8

In a vacuum stability test, five grams of the composition evolved 0.5ml. of gaseous decomposition products after heating for 40 hours at C.

Pellets of similar compositions containing artificially preparedmagnesium carbonate or calcium carbonate as cooling agent were extremelydifficult to ignite and were not capable of self sustained decompositionat atmospheric pressure. In the vacuum stability test 3.6 and more than15 ml. of gaseous decomposition products respectively were evolved from5 g. samples of these compositions after 40 hours at 100 C.

Example 2 A gas producing composition was made by intimately mixingtogether the following powdered ingredients:

Parts Guanidine nitrate 25.6 Ammonium nitrate 27.1 Potassium nitrate 2.8Dolomite 39.6

Oharges produced by pressing this composition at approximately 800 kg./sq. cm. supplied gases at a temperature of 800 C. and a pressure of 42kg./ sq. cm. and had a rate of reaction of 0.13 cm./ sec. when thereaction was initiated by local heating of a portion of the charge, atatmospheric pressure by means of an igniter composition yielding a hotslag. In the vacuum stability test, a 5 g. sample of the compositionevolved 1.5 ml. of gaseous products after 40 hours at 100 C.

Similar compositions containing artificially prepared magnesium orcalcium carbonates as cooling agents were incapable of self sustaineddecomposition and 5 g. samples of these compositions evolved more than15 ml. and 12.0 ml. respectively of gaseous decomposition products after40 hours at 100 C. in the vacuum stability test.

Example 3 A gas producing composition was made by intimately mixingtogether the following powdered ingredients:

Parts Guanidine nitrate 32.3 Ammonium nitrate 34.2 Potassium nitrate 3.8Magnesite 25.0 Ammonium dichromate 3.7 Copper oxide 1.0

Parts by volume at 20 C. Ammonia 0.9 Oxides of nitrogen 0.9 Carbondioxide 20.2 Oxygen 0.2 Hydrogen 2.4 Carbon monoxide 1.6 Nitrogen 73.9

A five gram sample of the composition evolved no gaseous decompositionproducts in the vacuum stability test after 40 hours at C.

Similar compositions containing artificially prepared calcium ormagnesium carbonate as cooling agent were incapable of self sustaineddecomposition at atmospheric pressure and 5 g. samples of the mixturesevolved approximately 8 ml. of gaseous decomposition products after 40hours at 100 C.

What we claim is:

A gas producing composition adapted to be compressed into pellets and ofpropagating self-sustaining non-detonating gas producing decompositionthroughout itself when locally heated consisting essentially of anoxidant selected from the group consisting of alkali metal nitrates andammonium nitrate, an organic fuel selected from the group consisting ofguanidine nitrate and nitroguanidine, a sensitizing agent selected fromthe group consisting of pulverulent copper, a copper compound, ohromatesand polychromates, and from 15 to 40% by weight of the total compositionof a naturally occurring carbonate of magnesium selected from the groupconsisting of magnesite and dolomite.

References Cited in the file of this patent UNITED STATES PATENTS988,858 Bronstein Apr. 4, 1911 2,159,234 Taylor May 23, 1939 2,481,795Taylor Sept. 13, 1949

